Fully realizing the vision of dynamic spectrum sharing (DSS) requires the adoption of fundamentally new spectrum access paradigms. This discusses taxonomy for classifying the threats. The taxonomy considers fundamental mechanisms for enabling coexistence as well as the points of attack with respect to the five‐layer protocol stack. For each threat category, representative security and privacy threats, and their relation to other types of threats are described. Furthermore, the chapter discusses the existing proposals for threat countermeasures and spectrum policy enforcement. It also discusses the research and regulatory challenges that need to be addressed to ensure policy enforcement in DSS. Building a complex enforcement framework will require a greater understanding of not only the engineering challenges, but also of the ramifications of the enforcement solutions in terms of legal, economic, and regulatory policy aspects.